Continuous flash coking process



June 19, 1956 J. w. SCOTT, JR

CONTINUOUS FLASH COKING PROCESS 2 Sheets-Sheet 1 Filed March 24, 1954 FIG.1

INVENTOR JOHN W. scorr, JR.

June 19, 1956 J, w, S JR 2,751,334

CONTINUOUS FLASH COKING PROCESS Filed March 24, 1954 V 2 Sheets-Sheet 2 RETORT GAS FEED II I" I I !!II 26 1 as INVENTOR JOHN W. 50077, JP.

2,751,334 CONTINUOUS FLAH COKING PROCESS Application March 24, 1954, Serial No. 418,316 6 Claims. (Cl. 196-65) This invention relates to a continuous coking process of the type wherein residual petroleum fractions are heated to convert a major portion thereof to lighter liquid hydrocarbon products, while the balance of the feed stock is left as coke. The particular process of this invention is one wherein the feed stock is continuously sprayed into a whirling stream of hot gases within a reactor in such a fashion as to effect a substantially instantaneous conversion of the feed to the desired end products, after which said products are rapidly and continuously withdrawn from the reactor.

Coking processes of one type or another have been practiced in the petroleum refining art for many years. A primary objective in all these processes has been to convert as large a proportion as possible of the feed stock (which is normally a heavy, tar-like residuum) to lighter hydrocarbon fractions while keeping coke formation to a minimum. The amount of coke formed by the coking procedures heretofore employed has ranged from about 1.8 to 2.5 times the value indicated for the particular stock by the Conradson carbon test, coking stocks normally having Conradson carbon values of from about 12 to 20. Since much of this coke is formed at the expense of the more desirable liquid hydrocarbon products, it is obvious that real benefit would accrue from any appreciable reduction in coke formation. Accordingly, it is a primary object of this invention to provide a continuous coking process which is characterized by the formation of relatively small amounts of coke and by an improved yield of lighter hydrocarbon products.

A further object of this invention is to provide a coking process wherein the gaseous and vaporous products recovered from the feed stock are of a higher quality than is possible with other types of coking processes. Thus, it is desired to provide a naphtha, or gasoline fraction, which is highly aromatic in character and has an aniiine point below 0-F., this in contrast to values of Well above 100 P. which are obtained with other types of coking processes from. comparable feed stocks. It is also desired to produce a gas oil fraction which has improved cracking qualities, and a tail gas stream which is high in oleiins rather than saturated hydrocarbons.

It has been found that the amount of coke formed dur ing the process is reduced and the quality of the hydrocarbon products improved as thermal cracking of the compounds present in the feed stock is reduced to a minimum. Accordingly, another important object of this invention is to provide a coking desired separation of hydrocarbons from the residual coke fraction by a method which reduces thermal cracking to a minimum.

The nature of still other objects of this invention will be apparent from a consideration of the descriptive portion to follow.

The present invention is based on the discovery that a wide variety of petroleum feed stocks, including those of a heavy, residual nature, can be continuously converted in good yields to vaporous (including gaseous) products of process which eliects the 2,751,334 Patented June 19, 1956 high quality, with relatively little, if any, coke being formed over and above the Conradson carbon values, by continuously spraying the liquid feed stock into the central portion of a whirling body, or vortex, of hot gases, hereinafter referred to as retort gases, which are introduced tangentially at the periphery of the generally cylindrical reaction zone. Here the spray particles are rapidly picked up by said gases and carried outwardly by centrifugal force towards the periphery of the reactor through progressively hotter retort gases. These gases act to strip the vaporous products from the feed particles, thereby coking the latter to dryness in a substantially instantaneous fashion. The volati'lized products obtained from the feed particles are then axially withdrawn from the reaction zone, along with the retort gases, in a rapid and continuous manner so as to minimize any further thermal cracking of said products.

The pressure to be employed in the reaction zone is not critical, and atmospheric, subatmospheric or superatmOS- pheric pressures can be used. Preferably, however, the process is conducted at atmospheric or slightly elevated pressures, as 5-30 p. s. i. g.

Temperatures prevailing in the reaction zone should be sufliciently high to effect coking of the given feed stock particles before the latter are thrown into contact with the wall forming the periphery of the reaction zone. Naturally, such temperatures will vary depending on both the composition of the feed stock as well as on the physical conditions prevailing in the system, i e., the diameter of the reaction zone, the speed of the whirling retort gases, the size of the spray particles, the position of the spray outlets, and other related factors. However, in the case of heavy residual petroleum stocks having ,API gravities of from about 0 to 20 degrees, which stocks are those most commonly subjected to coking procedures, the feed particles should be subjected to temperatures varying from about 800 to 1200 F, in regions near central portion of the reaction zone, to those of from about 14.00 to 2000 F., or even higher, in the regions adjacent the pcriphery of the reaction zone. in general, the temperatures in the reactor should be suf iciently high to effect readily coking .of the feed particles before they reach the periphery of the reactor, but not appreciably higher since the use of unduly high temperatures leads to an undesirable increase in thermal cracking of the hydrocarbon products recovered from theleed,

The heat in the reaction zone can be supplied in one or more of various ways. Thus, in the case where the retort gases, which are supplied at the periphery of the reaction zone in a tangential direction, contains substantially no oxygen (as is the case, for example, when tail gases are recycled to the reactor) the retort gases are preheated to the temperature which it is desired to maintain at the periphery of the reaction zone. On the other hand, when the retort gas is air or other oxygen-containing gas, part or all of the necessary heat can be obtained as a result of the combustion of a minor percentage of the feed stock products which will then occur. Additionally, the oxygencontaining retort gas stream may itself contain a combustible gas or minute coke particles, thereby minimizing the amount of feed products lost to combustion byproducts. In general, it is preferred to employ an oxygenconta'ining gas such as air as the retort medium, and to preheat the same to some temperature (e. g., 900 P.) which is intermediate between ambient temperature and that to be established at the peripheral or combustion zone within the reactor. Further, the feed stocks may be preheated to temperatures well above those necessary to effect the necessary fluidity to permit spraying, thereby supplying additional heat-t0 the reaction zone. Still other heating methods could beemployed either alone or in con 3 junction with the methods refererd to herein, one such alternative procedure, for example, being to supply external heat to the wall of the reaction chamber.

In carrying out the process of this invention, the throughput rate of the retore gases and of the volatile feed products in the reaction zone should be such as to provide a minimum residence time for said gases and volatile products in the zone. This time can vary from a fraction of a second to periods as long as a minute, though residence times of less than about 20 seconds are preferred in order to reduce thermal cracking reactions leading to an increase in the more volatile product gases at the expense of the heavier and more valuable gasoline and gas oil fractions.

The feed can be supplied to the coking, or reaction zone, at rates varying within a relatively wide range. Thus, for a given supply of retort gas, the rate at which the feed is introduced into the reaction zone can be varied from minimal values so low as to reflect an inefiicient method of operation to those so high as to result in inadequate removal of hydrocarbon product and the formation of improperly coked residual feed particles. The preferred practice is to introduce the feed at the maximum rate commensurate with efiicient removal of the desired hydrocarbon products from the feed particles and with the attendant formation of solid, non-tacky coke particles which can readily be removed from the reaction zone either by gravity and/or a suitable gaseous stream. The rate of feed supply which is preferred in any given system is a function of the various factors which affect the dynamics of that system, representative factors being the size of the feed particles and their composition, the dimensions of the reaction zone, and the amount, temperature and velocity of the incoming retort gases. However, with the heavier straight-run or cracked petroleum fractions (e. g., those having API gravities of from about to 20) which form the preferred feed stocks for use in practicing the present invention, effective separation of the hydrocarbon products, coupled with economical operation can be obtained by employing feed/ retort gas weight ratios having a value of from about 0.4 to 5, i. e., by the use of from 0.4 to parts by weight of feed for each part by weight of retort gas. With lighter feed stocks such as vacuum distillates, gas oils and waxes, good results can be obtained with still higher feed/retort gas weight ratios, e. g., those having values as high as about 7.

The foregoing paragraph has enumerated a number of difierent feed stocks which can be employed in this invention, and it may generally be stated that any feed material is suitable which is made up essentially of hydrocarbons and is capable of being sprayed into the reaction zone as a liquid. Numerous examples of particular feed stocks are given in the examples.

In the practice of this invention the feed stock to be coked is released in liquid particulate form through a spray nozzle or other distributing device positioned near the top of the reaction zone and on or near the central axis thereof, the velocity of said particles being such that they can readily be caught up by the whirling retort gases and rapidly coked to dryness before reaching the periphery of the reaction chamber. It is also possible to practice the present invention by releasing the liquid feed particles near the periphery of the reaction zone in such a fashion (usually at a relatively high velocity) that said particles reach the central portions of the reaction zone well before the major portion of the hydrocarbon products has been stripped therefrom. Once near the center of the reaction zone, the now decelerated feed particles are picked up by the whirling gas stream and coked to dryness in much the same fashion as in the case where the feed is released directly into the central portions of the reaction zone.

Having described the invention in general terms, attention is now directed to the accompanying drawings which illustrate the invention in various of its forms, the follow.- ing description also serving to explain more fully the coking and product separation features of this invention.

In the drawings:

Fig. 1 is an elevational view in partial section of a re actor suitable for effecting coking of admitted liquid feed particles;

F Figi 2 is a sectional view taken along the line 2-4 in Fig. 3 is an elevational view, somewhat schematic in character, of a modified form of a reactor vessel for the coking of admitted liquid feed particles; and

'Fig. 4 is a schematic view showing an over-all method of operation involving both coking of the feed particles, as well as the separation of the coke and hydrocarbon products formed during the coking step and a recycle of air pgrtion of the coke fines back to the reactor with the Referring now to Figs. 1 and 2 of the drawings, there is shown at 10 a generally cylindrical reaction chamber having side walls 11, a top 12, and a frustro-conical bottom portion 13 leading into a lock hopper 14 connected with coke draw-off line 15. The feed to be coked, which is normally in the preheated condition, is supplied through line 16 to the reaction chamber 10 where it is sprayed into the central portion of the reaction zone through nozzle 17. The latter, if desired, may be surrounded by a suit-; able blanket of steam (not shown) to reduce deposition of coke on the spray nozzle. The feed particles on being sprayed into the reaction zone are rapidly picked up and coked to dryness by the whirling stream of retort gases supplied through lines 18 to manifold 19 and directed tangentially into the reaction chamber by baffles 29; the arrangement of the battles within said manifold being particularly shown in Fig. 2. The retort gases along with the gaseous and vaporous products obtained from the feed particles and an appreciable amount of coke fines are axially discharged through line 21 at the top of the reaction chamber. The heavier coke particles formed in the reaction zone fall by gravity into the lock hopper 14 from which they are discharged through line 15.

In the modified form of reactor shown in Fig. 3 there is again shown a generally cylindrical reaction vessel 25 having a bafiied manifold 26 to which the retort gases are supplied through lines 27, the structure of said manifold and the nature of the baffie means therein being generally jected through spray nozzles 31 3 that of Fig. l in that leaving the reactor, as well as all of the coke particles the same as shown in detail in Figs. 1 and 2. Here, however, the feed can either be axially supplied to the reaction zone through line 28 and spray nozzle 29 (as shown in Fig. 3) or it can be supplied through lines 30 and inpositioned about the periphery of the reactor. Further, in either type of reactor unit, it is possible to employ both axial as well as peripheral means for introducing the feed spray. The form of reactor shown in Fig. 3 ditfers principally from here the gaseous components produced therein, are axially discharged downwardly from the reactor through line 32 rather than upwardly, as through line 21 in Fig. l. The effiuent materials in line 32 are discharged into a separator 33, preferably of cyclone I is not practical to separate type, from which the heavier coke particles and a substantial proportion of the coke fines are discharged through lock hopper 34 into line 35, while the gases and any remaining coke fines are discharged through line 36.

From the above discussion it will be seen that while it all the coke fines from the stream of product and retort gases by mechanical and/or gravity separation methods, nevertheless it is necessary to remove said coke fines from said gases before the latter can be usefully employed. While this separation can be effected by a number of difierent methods, it has been found that particularly good results are obtained by uti lizing a system of the type which is schematically presented in Fig. 4 wherein the fines remaining in the gaseous etiiuent stream from the reactor, after the practice of one or more mechanical separation steps, are washed out by contact with the incoming liquid feed stream and are then converted to larger particles as the feed is thereafter coked in the reactor. Referring now to the system which is schematically presented in Fig. 4, the feed to be coked is shown as entering through line 40 from whence ti is discharged into a fractionating column 41 at a point well above that at which the stream of fines containing retort and product gases enters the column through line 42. The liquid fuel passing downwardly through the column washes out the coke fines from the incoming gas stream and is discharged from the bottom of the column through line 43. A portion of the feed in. said line 43 can be recycled, if desired, back to the column through line 44 and optionally through line 45 into the product line 42. The balance of the feed discharged from the column through line 43 is recycled to reactor 46, preferably through furnace 47 which serves to preheat the feed to any desired temperature before the latter is sprayed into the reactor 46. The feed sprayed into said reactor 18 rapidly coked to dryness under the influence of the hot retort gases which enter the system through line 48 which preferably passes through furnace 47 to preheat .the gases and from which the heated gases are now tangentially discharged into reactor =36 through the bathed manifold 49. The heavier coke particles formed in the reactor (in. part from the coke fines in the feed stream) are discharged at the bottom of the reactor through lock hopper 50 and are carried out of the system through line 51. On the other hand, the retort and product gases, along with an appreciable content of coke fines, are carried upwardly from the reactor through line 52 and into a cyclone type of separator 53 which separates out a portion of the coke fines and discharges the same downwardly through lock hopper 54 into line 55. The remaining fines, along with the product and retort gases, are discharged from the separator through line 42 into the column 41 from which the retort gases and lighter hydrocarbon products formed in the reactor 46 are discharged through line 56 While the heavier product fractions are discharged through lines 57 and 58. Any remaining, still heavier product compound is recycled back to the reactor along with the feed through line 43-.

While the system of Fig. 4 is illustrated in connection with an up-flow coking reactor of the type illustrated in Fig. 1, it is obvious that the process is equally well adapted for use with a reactor ot the modified type shown in Fig. 3.

The process of this invention is illustrated in various of its embodiments in the following examples.

Example 1 In this operation, conducted in accordance with the process described in Fig. l, a feed stock made up of Bose-an residuum having the properties,

is preheated to 900 F. and sprayed at a rate of 2800 lbs/hr. into the coking reactor vessel. Air, employed as the retort gas, is supplied to the reactor at a temperature of 945 F. at an air/feed weight ratio of 0.41, the size of the reactor being such as to provide an average residence time for the retort and product gases therein of from about 2 to 4 seconds. Of the feed supplied to the reactor, approximately 3.2% by weight is burned under these conditions, thereby providing a temperature near the periphery of the reactor zone of approximately 2100 F., while that of the outlet gases is approximately ll.F. The pressure employed in the system is 50 p. s. i. Analyses of the various gas, liquid and coke products obtained by coking of the feed stock in this operation discloses the following product distribution in terms of weight per cent.

Total C2 and lighter 7.5 Total C: 2.5 Total Cs 2.2 Total C5 1.5 Gasoline fraction (Cs-400 F., 37 API gravity, and.

blendedaniline point of -4-i)) 11.1. Gas oil fraction (400 F.+, 16 API gravity) 59.0 Coke 1.3

The individual coke particles recovered from the above operation vary in size from about 20 to microns in diameter and appear to be made up in large proportion of hollow spheres and sphere fragments, the coke having a bulk density of about 2.3 lbs/cu. ft.

Example 2 procedure outlined in Example 1 is repeated under generally the same conditions, but with 014 pounds of steam per pound of feed being supplied along with the air, which in this case is preheated to 865 F. and supplied in the amount of 0.34 pounds per pound of feed. Here the total amount of C2 and lighter products recovered is 2.9%; the Css total 1.7%; the Css total 017%; the C5S total 0.5 5%; the gasoline fraction, 11.1%; the gas oil fraction, 67.7%; and the coke fraction is 13.2%, approximately 2.35% by weight of the feed being burned in the reactor. The character of the gasoline and gas oil fractions is generally the same as that noted above in Example 1.

In this operation the Example 3 in this operation, wherein there is employed the same feed stock and other conditions as described above, the process employed is that of the type illustrated in Fig. 4. Here it is found that once equilibrium conditions are es tablished in the system, the feed to the reactor contains about 1% by weight coke fines. Further, due to the fact that. a certain amount of the heavier coking hydrocarbon products are recycled to the coking zone, the total amount of C5 and lighter products is increased to about 1.6% while the gasoline fraction is reduced to 10.8% and the gas oil fraction to 57%.

Example 4 In this operation there is again employed the modified form of operation described in Example 3 above except that here the necessary amount of coke was burned to preheat the fuel and the inlet stream of air and steam retort gases to the desired inlet temperatures of 900 F. and 865 F., respectively. This has the eiiect of reducing the net yield of coke from I3 to approximately 10%.

Example 5 The process described in this example is carried out with a reactor of the type illustrated in Fig. 1, said reactor having a volume of approximately three cubic feet. In: this operation. a. feed made up of a Santa Maria residuum having the following characteristics,

Gravity, API 9 Sulfur, weight percent 5.34 Viscosity, SSU at F 36,000 Conradson carbon value, weight percent 11 is sprayed into the reactor at a rate of 56.5 lbs/hr. and at a temperature of approximately 300 F. Air, at room temperature, is supplied to the reactor in the amount of 1.62 pounds per pound of feed, this amount of .air serving to permit combustion of approximately 15.5% of the feed in order to supply the heat necessary to effect coking of the sprayed feed particles, the temperature at the reactor periphery being approximately 2000" F. and that at the gas outlet being 1025 F. In this reaction it was found that of the gaseous products formed, the total weight percent of the C2, C3 and C4 products was approximately 25%, while of the liquid products boiling above200" F to be made up essentially of hollow spheres and sphere fragments. It had a bulk density of 2.5 lbs/cu. ft.

Example 6 This operation is conducted using the same type of equipment as that referred to above in connection with Example 5, except that here the feed is a catalytic cycle oil having the following characteristics:

Gravity, APl 24.3 Viscosity, SSU at 130 F 48.9 Pour point, P. 65 Aniline point, F. 64 Conradson carbon value, weight percent 0.18 Boiling range, ASTM D-158:

Start, F. 568 608 50% 663 95% 748 End point 760 Operating conditions for this run are as follows: Feed rate, lb./hr. 107 Periphery temp, F. 1200-1400 Product steam temp, F 1070 Feed burned in reactor (percent) 8.5 Air rate, lb./hr. 107 Steam, lb./hr 22.5 Air-steam temp. at inlet, F. u 850 Analysis of the products reveals that the 410 F. end point gasoline has an aniline point (blended) of -77 R, an API gravity of 31.7, and a bromine number of 62. Conventional adsorption analysis indicates that this gasoline contains 79% aromatic hydrocarbons, 14% aliphatic olefins and 7% paralfins and naphthenes. Finely divided, free-flowing coke was recovered in the amount of about 0.23%, based on feed weight. Analysis of the raw product gas was as follows:

CO 5 .7 N2 59.3 Oz 0.3 Hz 9.8 CH4 8 .8 CaHz 0.7 Cal-I4 5 .8 CzHs 0.3 CO2 7.5 CaHa 1.1 CsHs 0.2 CeHa 0.5

This run specifically demonstrates that valuable aromatic and unsaturated hydrocarbon products are produced when a petroleum fraction of negligible Conradson carbon is .used as the feed.

In the foregoing examples reference has been made to the fact that the majorportion of the coke produced was made up of minute, thin'walled,-hollow globules, or ccnospheres or of fragments-thereof. These coke particles, which are useful in a wide-variety of applications such as for insulation and to provide a floating protective coating over liquid surfaces to' cut down evaporative losses, normally vary in diameter from about 20 to 200 microns, the wall thickness of the coke particle being less than onetenth that of the particle diameter in most instances. The density of these coke particles varies from about 2 to 3 lbsz/ cu. ft. andjnor rnally lies in the range of 2.'3 to 2.7

lbs/cu." ft.

1. In a continuous coking process wherein a liquid petroleurn feed stock is thermally converted into a vaporous hydrocarbon fraction and a particulate coke fraction, the steps comprising tangentially introducing a stream of oxygen-containingretort gases in continuous fashion at the periphery of a generally cylindrical, heated reaction zone while continuously withdrawing gaseous and vapor ous eflluent from the axial portion of the zone, thereby establishing a whirling body of hot retort gases in the re action zone; continuously introducing a petroleum feed stock in liquid particulate form into a central portion of said whirling body of retort gases whereby the liquid feed particles are picked up by said gases and carried outwardly by centrifugal force toward the periphery of the reaction zone, the temperature of said retort gases being sufiiciently high to rapidly effect the desired thermalconversion of the feed particle into the respective vapor and coke product fractions during said outward movement; and continuously discharging the hydrocarbon and coke fractions obtained from the feed axially with respect to the reaction zone, said process being characterized by the maintenance of a combustion zone adjacent the periphery of the reaction zone to supply at least a portion of the heat required to effect thermal conversion of the feed.

2. The process of claim 1 wherein the vaporous product fraction, along with the stream of retort gases and a portion of the coke fraction, is axially discharged from the reaction zone as an upward efiiuent stream, while the balance of the coke is discharged axially downward from the said zone.

3. The process of claim 1 wherein the vapor and coke product fractions, along with the stream of retort gases, are axially discharged from the reaction zone as a downward effluent stream.

4. A process of converting high boiling residual petroleum crude fractions by heat treatment into lighter hydrocarbon fractions of improved characteristics and solid particulate coke which comprises introducing an oxygencontaining retort gas into a heated reaction zone of cylindrical configuration in a generally tangential direction at a peripheral inlet and withdrawing gaseous and vaporous effluent from the axial portion of the zone thereby main taining a vortex movement of the flowing gas intermediate said peripheral inlet and axial outlet, feeding said crude fraction into the central portion of the gaseous vortex as discrete liquid particles of mass and size such as to be impelled to travel transversely through the vortex of retort gas toward the periphery of the reaction zone, the rate of movement of the vortex and size of particles being correlated to maintain said transverse movement of the particles through the heated reaction zone for a period of time sufiicient to accomplish the desired thermal conversion thereof,said process being characterized by the maintenance of a combustion zone adjacent the periphery of the reaction zone to supply at least a portion of the heat required to effect thermal conversion of the feed,

5. In a continuous coking process wherein a liquid petroleum feed stock is thermally converted into a vaporous hydrocarbon fraction and a particulate coke fraction, the steps comprising introducing a liquid pelroleum feed stream into a fractionating column; withdraw ing-a liquid bottoms stream from said column and spray ing said stream into the central portion of a generally cyf lindrical, heated reactor; rapidly converting the outwardly moving spray particles in the reactor into a vaporous product fraction and a particulate coke fraction by contacting said particles with a stream of hot oxygen-containing retort gases introduced tangentially at the periphery of the reactor; axially discharging said retort gases and said vaporous product fraction as a common effluent stream from said reactor along with at least a portion of the coke fraction; introducing said eflluent stream into said fractionating column at a point below that at which the feedstream is introduced whereby any coke fines remaining in the efiduent stream are removed by the downcoming liquid feed stream; and removing the retort gases and the vaporous product fractions obtained in said reactor from the fractionating column.

6. The process of claim 5 wherein the efiiuent stream from the reactor is subjected to a de-coking operation before being introduced into the fractionating column.

UNITED STATES PATENTS Hemminger June 24, 1941 Hemminger Nov. 21, 1944 Wells Dec. 23, 1952 FOREIGN PATENTS Great Britain Jan. 26, 1928 Great Britain Apr. 12, 1928 

1. IN A CONTINUOUS COKING PROCESS WHEREIN A LIQUID PETROLEUM FEED STOCK IS THERMALLY CONVERTED INTO A VAPOROUS HYDROCARBON FRACTION AND A PARTICULATE COKE FRACTION, THE STEPS COMPRISING TANGENTIALLY INTRODUCING A STREAM OF OXYGEN-CONTAINING RETORT GASES IN CONTINUOUS FASHION AT THE PERIPHERY OF A GENERALLY CYLINDRICAL, HEATED REACTION ZONE WHILE CONTINUOUSLY WITHDRAWING GASEOUS AND VAPOROUS EFFLUENT FROM THE AXIAL PORTION OF THE ZONE, THEREBY ESTABLISHING A WHIRLING BODY OF HOT RETORT GASES IN THE REACTION ZONE; CONTINUOUSLY INTRODUCING A PETROLEUM FEED STOCK IN LIQUID PARTICULATE FORM INTO A CENTRAL PORTION OF SAID WHIRLING BODY OF RETORT GASES WHEREBY THE LIQUID FEED PARTICLES ARE PICKED UP BY SAID GASES AND CARRIED OUTWARDLY BY CENTRIFUGAL FORCE TOWARD THE PERIPHERY OF THE REACTION 